The macula is the part of the retina which is responsible for central vision. Age-related macular degeneration is a chronic eye disease that occurs when tissue in the macula deteriorates. Macular degeneration affects central vision, but not peripheral vision. Macular degeneration is the leading cause of severe vision loss in people age 60 and older.
There are two forms of age-related macular degeneration: dry and wet. Dry macular degeneration is the most common type of macular degeneration and occurs when cells of the macula slowly begin to break down. Yellow deposits called “drusen” form under the retina between the retinal pigmented epithelium (RPE) and Bruch's membrane, which supports the retina. The drusen deposits are debris associated with compromised cell metabolism in the RPE. Eventually there is a deterioration of the macular regions associated with the drusen deposits resulting in a loss of central vision.
Wet macular degeneration occurs when abnormal blood vessels grow behind the macula. These vessels are fragile and can leak fluid and blood, which result in scarring of the macula and raise the potential for rapid, severe damage. Bruch's membrane breaks down, usually near drusen deposits. This is where new blood vessel growth, or neovascularization, occurs. Central vision can become distorted or lost entirely in a short period of time, sometimes within days. Wet macular degeneration is responsible for about 10 percent of the cases of age-related macular degeneration, but it accounts for about 90 percent of the cases of legal blindness.